1. Field of the Invention
The present invention relates to an EPDM foam, a sealing material including the EPDM foam, and a producing method of the EPDM foam. More particularly, the present invention relates to an EPDM foam which is used suitably as a sealing material for various industrial products, a sealing material including the EPDM foam, and a producing method of the EPDM foam.
2. Description of the Related Art
Conventionally, as a sealing material for various industrial products, an ethylenepropylenediene (hereinafter referred to as EPDM) foam has been known in terms of durability, which is obtained by foaming an EPDM rubber with a foaming agent.
In such an EPDM foam, in addition to a foaming agent, a vulcanizer for vulcanizing EPDM and a vulcanization accelerator for accelerating the vulcanization of EPDM are blended. As vulcanization accelerators, secondary amines are used frequently. However, when secondary amines are used, nitrosamines (N-nitrosodimethylamine, N-nitrosodiethylamine, and the like) may be generated.
Accordingly, as an EPDM foam capable of reducing the generation of nitrosamines therefrom, there has been proposed a foam rubber using, for example, a vulcanization accelerator (N,N′-ethylenethiourea, 2-mercaptobenzothiazole, diphenylguanidine, tetrakis(2-ethylhexyl)thiuram disulfide, or zinc dialkylthiophosphate) free from the possibility of generation of nitrosamines (see, for example, Japanese Unexamined Patent Publication No. 2006-225415).